Monday, September 14, 2009

Crawfish (or crayfish) have social,economic and ecological significancein several regions around the world,including the southern United States.Louisiana dominates the crawfishindustry of North America in bothaquaculture and wild capture fisheries.Crawfish also are cultivated forfood in Texas, Arkansas, Mississippi,Alabama, South Carolina and NorthCarolina, and are consumed in theseand many other states. However,there is no place where crawfishhave had more impact on the economyof a region than in Louisiana,where the industry contributes wellin excess of $150 million to thestate’s economy annually.Species of importanceProcambarus clarkii (the red swampcrawfish) and P. zonangulus (thewhite river crawfish) are the speciesof greatest commercial importance inthe southern U.S. Procambarus acutusacutus, sometimes referred to as theeastern white river crawfish, is cultivatedin several states along the eastcoast of the U.S. and is nearly indistinguishablefrom P. zonangulus.These crawfishes belong to the phylumArthropoda (subphylumCrustacea), order Decapoda, andfamily Cambaridae. The red swampcrawfish is native to the states borderingthe Gulf of Mexico from Texasto Alabama, northward up the MississippiRiver drainage into Tennesseeand Illinois, and southward into easternMexico. The red swamp crawfishhas been introduced in other areas ofthe U.S. (including Hawaii) and in atleast 19 other countries in Centraland South America, the Caribbean,Europe, Africa and Asia. The whiteriver crawfish is found in the southernstates along the Gulf of Mexicoand northward up the MississippiRiver drainage, possibly as far as theconfluence of the Mississippi andOhio Rivers. The eastern white rivercrawfish is found along the Atlanticcoastal plain into southern NewEngland.The red swamp and white rivercrawfishes, and to a lesser extent theeastern white river crawfish, havesimilar ecological requirements. Thered swamp and white river crawfishesoften co-exist in the same nativehabitat or managed impoundment.Both are ecologically adapted to theannual hydrological cycles of springflooding and summer dry periodscommon to large river systems andfloodplains in the region. Bothspecies construct simple shallow burrows,to which they retreat to reproduceand survive temporary dry periods.One notable difference betweenthe two species is that, in the South,the white river crawfish is a seasonalspawner, reproducing only in the falland winter. Red swamp crawfish mayspawn at any time during the yearwhen environmental conditions arefavorable. The red swamp crawfishproduces more, but smaller, eggsthan the white river crawfish. Thered swamp crawfish appears to bebetter adapted to nutrient-rich watersand may tolerate higher water temperatures,although these differenceshave not been confirmed. The whiteriver crawfish grows faster at coolertemperatures and can attain a slightlyhigher maximum size of about 130grams (3.5 crawfish per pound).Anecdotal evidence indicates that thered swamp crawfish is usually moreabundant in standing water habitatswith low dissolved oxygen, such asswamps. Hence the common namered swamp crawfish.Both red swamp and white rivercrawfishes do well in commercialcrawfish ponds, and both thrive inthe low-energy-input, extensive aquaculturesystems used in Louisianaand other southern states. Thoughthe abundance of each species canvary among ponds and within a pondduring the 7- to 10-month productioncycle, the red swamp crawfish mostoften dominates the catch and is themost desired species in the marketplace,particularly in Louisiana.White river crawfish are usuallymost numerous in ponds that havebeen in continuous cultivation forseveral years; it occasionally becomesthe dominant species over time.The factors that govern the relativeabundance of the two species inproduction ponds are not fullyunderstood. Research has shownthat the species that enters the

The profitability of redclaw aquaculture has been assessed using a model or hypothetical farm, with data gathered from several farms and two pilot-scale commercial farms established jointly by the participating farmer and DPI.The model involves a farm size of 40 x 1000 sq.m growout ponds and 7 x 1000 sq.m juvenile production ponds, representing a total pond area of 4.7 hectares.Previous analysis (Hinton, 1994) suggested that a production area of approximately four hectares was the minimum for commercial viability of a stand alone redclaw farm.The financial evaluation was undertaken using a discounted cash flow technique. Discounting was used to allow for the timing of the costs and benefits for the life of the enterprise which was assumed to be 20 years (Johnston and Jones, 2001).The model farm was assumed to annually harvest 394 kilograms of redclaw per growout pond from year two onwards.Redclaw were estimated to take nine months to reach the acceptable market size of 65 g mean weight. At this weight the farmgate price was estimated to be AUD13.50 per kilogram.Initial establishment of the model farm was estimated to cost AUD347,900. Included in this cost were land, hired labour, machinery and all farm infrastructure costs.Specifications for the farm layout and pond characteristics were based on 'best practice' recommendations (Jones and Ruscoe, 1996).Redclaw aquaculture was profitable based on the model farm.Using the model farm yield and price, the farm profit was AUD5.25 per kilogram each year. The total costs of production were estimated to be AUD 8.25 per kilogram each year. Included in this cost were all operating costs, capital costs and allowance for the owner's labour and management.The discounted payback period, which represents the time to recover the initial outlay, was four years.Sensitivity analyses for prices and yield showed that, at the annual yield of 394 kilograms per growout pond, the minimum price for the investment to be profitable was AUD8.25 per kilogram.Similarly, at the assumed price of AUD13.50 per kilogram, the minimum annual yield required to be profitable was 232 kilogram per growout pond.Growout periods may vary between 6 months and 15 months depending on the redclaw market weight the grower intends selling.Redclaw market weights and price were assumed to increase with longer turnoff periods.Based on a sensitivity analysis which compared various growout periods, the most profitable option was nine months.The least profitable turnoff period was 12 months. The results from this analysis were very sensitive to prices, survival rates and market weights.Survival rates and market weights are strongly correlated to farm management expertise.Results from established farms applying best practice techniques confirm that the economics of the model are a true and accurate representation of commercial redclaw aquaculture.

Redclaw is a tropical species endemic to north-west Queensland and the north-east of the Northern Territory. The harsh physical extremes of this distribution have given redclaw a robust nature with broad climatic tolerances.Its preferred temperature range (water temperature) for >70 percent of maximum growth rate is 23ºC to 31ºC. Temperature extremes beyond which redclaw will perish are 10ºC and 36ºC.Reproduction will only occur while water temperature remains above 23ºC. While suitable temperatures prevail throughout Queensland during summer, the shorter and less extreme winter period in more northern areas confers a significant advantage.Most industry growth is expected to occur north of Bundaberg, including parts of western Queensland, northern Northern Territory and the Kununarra region of Western Australia.This map broadly indicates the regions suitable for redclaw production.Redclaw aquaculture necessitates earthen ponds which hold water. Consequently, soil must have a reasonable clay content and be free of rock. Ponds are typically 1,000 sq.m in surface area, with a depth of between 1.0 and 2.5 m. Their specification and design can have an important bearing on productivity, so professional advice should be sought prior to construction.Productive topsoil can be beneficial when applied across the clay-base of a pond, but it must be free of pesticides which may be highly toxic to crayfish. Water may be sourced from surface supplies or underground. Generally, water suitable for watering livestock is suitable.Some of the characteristics which should be identified include;pH of between 6.5 and 8.0,hardness of >40 ppm,low salt contentand low metals content.Once water has been introduced to the production ponds there are a host of management issues which must be addressed to ensure optimal water quality for redclaw production.Further information on water quality management should be sought. Water usage is dependent on local evaporation rates, but will range from 15 to 20 megalitres per hectare of ponds. This is on the basis that all effluent from harvested ponds is recycled through appropriate settlement and supply dams.Varieties/breedsResearch has demonstrated that distinct strains of redclaw occur throughout the species natural range. The differences between strains are generally slight, however, variability of biological characteristics as borne out in production statistics suggests that some strains are superior for aquaculture purposes. Although the full range of strains have not been assessed, it is clear that the Gilbert and Flinders River strains have advantageous characteristics in regard to high fecundity (number of young per brood) and fast growth rates at high densities.Some long-standing redclaw farmers have selectively bred their perceived 'best' crayfish and cross-bred strains to improve their stock. There are clear indications that these improved stocks are superior to wild undomesticated stock and to stock from farms where managed reproduction has not occurred.A managed selection program for increased growth rate of redclaw established by the Queensland Department of Primary Industries in 1993, has successfully increased growth rate by about 45 percent to date. This program is continuing and now produces improved 'Walkamin' stock for distribution to industry from the Freshwater Fisheries and Aquaculture Centre at Walkamin.Animal husbandryOnce all government approvals have been sought and an aquaculture license has been issued, the farmer may acquire crayfish from established growers or from the DPI.Stock may be purchased as broodstock and used to generate juveniles for stocking to the new operation, or as juveniles for immediate stocking.The husbandry involved is best explained in terms of the key elements of recognised 'best practise'.Site selection is the first step, and should involve assessment of several criteria which will maximise the suitability of the chosen site.A designed and systematic farm layout is important to minimise establishment and operational costs by utilising gravity to fill and drain ponds, and to centralise facilities.Optimal pond specifications are 1000 sq.m , 1.2 to 2.5 m in depth and a V-shape that allows rapid and complete drainage.Artificial shelters for the crayfish are essential. They should be abundant, and their shape, specification and positioning should permit water to drain out freely and completely as the pond is drained. Thick bundles of synthetic mesh and/or stacks of pipe material have been found to be the most effective.Aeration is also essential. For redclaw aquaculture it is most often provided through airlift pumps, although other forms of aeration such as paddle-wheels and aspirators may be used. The aeration system should provide both oxygen input to the water and circulation of water from bottom to top and around the pond.Juvenile production and growout of stock to market size are managed as separate processes. A managed juvenile production program is essential to provide the advanced juveniles required for growout, and to make effective use of the superior broodstock selected. Depending on temperature and whether berried females or mature broodstock are used, a culture period of 3 to 4 months is necessary to achieve a mean size of juveniles of 5 to 15 g. The two most critical factors in juvenile production are shelter and food.Growout also involves an active stock management approach. Because redclaw breed so readily and profusely, the pond populations must be managed intensively. This includes stocking with known numbers of advanced juveniles of at least 5 g mean weight. Uniformity of size is very important. Maximum size range at stocking should be 10g. Stocking density of between 5 and 15 per sq.m is recommended.The food used will have an important bearing on production. Several commercial crayfish pellets are available, which have proven to be effective. Chicken layer pellets are not recommended. The most effective diets have a protein content of approximately 20 percent and are composed primarily of grains. A feeding frequency of once per day is recommended, preferably at dusk when crayfish are active. Use of a feeding schedule and feed trays is critical.Active management of the pond environment is integral to commercial yields. There should be weekly monitoring of pH, dissolved oxygen and secchi; monthly monitoring of hardness, alkalinity and ammonia. All measurements must be made at the water / soil interface on the bottom, and some contingency plan must be developed to counter water quality which falls outside of preferred ranges. This may involve applications of lime or fertiliser, or flushing of the pond with fresh water.Drying of ponds between crops is essential to sterilise and re-vitalise the bottom. There is often a considerable build-up of organic waste after a culture period. The most effective management of this is to dry the pond for 1 to 2 weeks until cracks appear. Toxic compounds are broken down and useful nutrients are released.Protection against birds, rats, and eels, and any other potential predators must be provided. Complete enclosure netting and fencing is essential. Economic analysis indicates that the cost of netting (including materials and installation) is equivalent to about 15 percent of one crop. As losses to predators may be well in excess of this, netting is very cost-effective.Provided good husbandry practices are applied both processes of juvenile production and growout can be completed within 12 months.Disease controlSeveral potentially disease causing organisms including protozoans and viruses have been identified in redclaw.To date none have caused any significant commercial loss, and industry are aware that careful quarantining and good health monitoring and management will minimise the risk of a disease outbreak.A virulent disease of crayfish which has decimated production throughout Europe is known as 'crayfish plague'. Australia is free of this disease, and authorities are conscious of the importance of preventing its entry into the country.By maintaining good culture conditions which maximise survival and growth, stress of crayfish is minimised and the threat of disease is relatively small. Because production of juveniles and growout are contained on each farm, there is little requirement to introduce new, potentially disease-carrying stock to the farm. This factor also diminishes the risk of disease.Harvest, processing and packagingHarvesting is generally quite straightforward, however if it is not managed carefully, the previous several months of production management can be wasted.Some form of sampling prior to harvest is important to gauge the size and number of crayfish expected.Harvesting may involve a number of methods, although the most effective is the application of a flow-trap. This trap exploits redclaw's strong response to flowing water. A slow but steady flow of water into the pond via a box and ramp will illicit movement of crayfish against the flow and into the box. Flow-trapping should involve 95 percent drainage of the pond over 24 hours from dawn to dawn. There should be several thousand litres of water remaining in the deepest part of the pond at dawn, when stock are removed.The slow drainage enables the crayfish to move out of shelters and with the main body of water, so they concentrate and respond most effectively to the flow trap. Both the flow trap and the last remaining water must be well aerated. The entire harvest can be easily lost if the flow trap or remaining pond water are not aerated. The stock should be quickly removed and transported to clean water in a tank system.Care should be taken to minimise crushing by not exceeding 15 kg of stock per transport container.Other harvesting methods include bait trapping and drain harvesting with manual collection of stock.The majority of redclaw are sold live, and so after harvesting stock are held in tanks with flow-through water supply or a recirculating system involving biological filtration.A period of at least 24 hours in the tank to permit purging of the gut is recommended prior to packing for transport.Redclaw can survive extended periods out of water provided they are kept cool and moist. Packing therefore involves insulated containers containing some moist packing material (foam rubber or wood shavings) and cooling packs.Road transport is used for local markets, however air transport is necessary to the large seafood markets in Sydney, Melbourne and for export.

Redclaw, Cherax quadricarinatus, is a species of freshwater crayfish native to the rivers of north-west Queensland and the Northern Territory.Although well known to the locals of this isolated region of tropical Australia, it remained effectively unknown to the rest of Australia until the late 1980s. It was at that time that the first tentative steps were taken to farm freshwater crayfish in Queensland, although initially the endeavours were applied to an imported species, the marron, from Western Australia.It was abundantly evident after a short period that the cool-water marron was unsuitable for Queensland conditions, and the native redclaw was suggested as an alternative.Redclaw proved to be well suited to cultivation, and the Redclaw Aquaculture Industry was born, developing quickly and spreading throughout Queensland, south to NSW and westwards into the Northern Territory. Now, 15 years on, the industry has a solid foundation and has runs on the board, reflecting its commercial viability and potential for substantial growth.Redclaw is advantaged by a host of physical, biological and commercial attributes which make it an excellent candidate for aquaculture.It is a physically robust species with broad geographic potential, has a simple life-cycle and straight-forward production technology, requires simple foods and is economic to produce.The texture and flavour of the flesh compares very favourably with other commonly eaten marine crustaceans, and having the appearance of a lobster, is positioned at the premium end of the crustacean market spectrum.While current production at around 80 tonnes per annum is primarily marketed domestically, the growth potential for the industry lies with the substantial export demand for this product.Given that viable production technologies are now established, the challenge for the industry is to increase production, through expansion and new investment, to lift production volumes to a point where the substantial quantities required by identified export markets can be consistently supplied.Although a native Australian, redclaw's excellent aquaculture attributes have seen it exported to several other countries where commercial production has now been established. In the short-term this will be to Australia's advantage in increasing the market profile of this new product.Longer term, Australia will maintain a production advantage based on access to the broad genetic pool of native stocks, sustainability due to thorough environmental regulations and isolation from recognised diseases which have decimated off-shore industries.Redclaw aquaculture in Australia is poised for significant expansion. The basic resources of suitable land and water are readily available throughout northern Australia, and could potentially support production of several thousands of tonnes. Production technologies are now well developed, and 'best practice' methods have been defined.These technologies are relatively straight-forward and the skill levels required of practitioners are not onerous. Nevertheless, a background in farming and/or qualifications and experience in aquaculture are a distinct advantage.Good supporting documentation and training are readily available. The challenge for the industry is to increase production, through expansion and new investment, to lift production volumes to a point where the substantial quantities required by domestics and export markets can be consistently supplied.Markets and marketing issuesThe Redclaw industry is faced with several marketing challenges.Typical of most fledgling industries, very little promotion has been undertaken, thus consumer awareness both domestically and overseas is relatively low.The industry is composed of a great number of small enterprises making the marketing quite fragmented. Recently, localised marketing groups have emerged consisting of several cooperative growers with common purpose. They have established quality standards, brand names and promotional material to more effectively market their collective production in a coordinated manner.In Australia Redclaw are commonly marketed in 20 g size grades ranging from 30-50 g (at approximately AUD11.50/kg) to greater than 120 g (at approximately AUD19.00/kg). The smaller grades are commonly used in buffet style presentations, with the larger animals featuring in a-la-carte restaurants, both as entree and main course dishes.Export opportunities have been identified through considerable market research. However, sales to date have been limited by the small production volume and therefore the risk of inconsistent supply.At present 50 percent of redclaw are sold within Queensland, 45 percent interstate and 5 percent are exported.There are three steps in the marketing chain; producer, wholesaler and restaurateur. There is effectively no retail sale of the raw product. While selling direct to restaurants may result in slightly higher prices paid, the practise can have a limiting effect on market growth. A good wholesaler can increase the market penetration of Redclaw by cross-selling while servicing customers from their existing product lists. Farm-gate sales are substantial, however, the volumes are likely to decrease as more coordinated marketing through wholesalers develops. Wholesalers have tended to position Redclaw on the price scale lower than marine lobsters but higher than prawns.Generally they are marketed alongside Moreton Bay bugs and small champagne lobsters or scampi. A clear marketing attribute for redclaw is its reputation as a product from clean water, free of medical or chemical additives. Product is purged prior to sale and is often held in saltwater which improves the flavour and its attractiveness to Asian markets.Redclaw are largely sold as a live product, although some processing, particularly cooking and freezing is undertaken. Fresh redclaw have a smooth lustrous shell, deep blue to green in colour, with males exhibiting a bright red colouring on the margins of their large claws. Cooked, they present as bright red, typical of premium crustaceans.

Redclaw female with eggs. One of the primary advantages of redclaw for aquaculture is the lack of free-living larval stages, and therefore absence of a hatchery phase.

Redclaw juveniles being harvested using a flowtrap at the Jennings farm near Mareeba.

Aquaculture technicians inspecting tagged crayfish as part of a farm trial to assess the performance of an improved stock developed at Freshwater Fisheries and Aquaculture Centre Walkamin

DPI Aquaculture technician, Jo Grady, measuring water quality in a redclaw pond at Walkamin Research Station

Cage research facility at Freshwater Fisheries and Aquaculture Centre ,Walkamin, used for redclaw experiments concering breeding, nutrition and husbandry. Redclaw in a flowtrap. The flowtrap was developed at Freshwater Fisheries and Aquaculture Centre, Walkamin as an aid in harvesting. It provides a simple, effective and efficient means to harvest stock from ponds with minimal labour and which results in high quality product